A terahertz wave is between a millimeter wave and an infrared wave and thus not only has a certain penetration ability like the millimeter wave but also has a relatively high resolving ability like an infrared wave. Thus, a terahertz wave can be used in security inspection of baggage, packages or other items as well as human body security inspection. Applications of the terahertz wave have developed gradually. However, there is currently lacking a method of efficiently generating a terahertz wave and an accurate detecting method using a terahertz wave. A terahertz detector is needed to be studied continuously.
Detection using a terahertz wave may be classified into two technology types, i.e., one is coherent detection and the other is non-coherent detection. Due to low output power of terahertz radiation, loss of transfer, heat radiation, noise, etc., a terahertz signal that is detectable is rather weak. Thus, there is a dire need for a terahertz detector with high sensitivity for the development of terahertz technology. In this context, many types of terahertz wave detectors are being developed. A heat radiation meter is a non-coherent detector that can detect power of radiation and is not able to report phase information. Further, this type detector commonly works at a low temperature in order to reduce detection noise. A pyroelectric transducer has a relative simple structure and operation, and may work in normal temperature. However, a response time of a pyroelectric transducer depends on a process of establishing a new balance temperature, that is, a pyroelectric transducer cannot detect a terahertz signal during changing of temperature. A Golay detector has a wide response frequency band, a low equivalent power of noise, a high response sensitivity and may operate at normal temperature. However, the Golay detector is sensitive to vibration and has bad stability as a whole. In addition, there is a counting type terahertz detector, such as a single electron transistor detector and a quantum cascade laser, which is mainly used to detect photons at a frequency of more than 1 THz while having no effect for a low energy photon at a frequency less than 1 THz. Further, the whole apparatus for a counting type terahertz detector is very expensive and needs to work at a super low temperature, and thus has a limited ability to be widely used.